1. Field of the Invention
The present invention relates to a method and apparatus for cleaning the atmosphere; and more particularly to a stationary substrate comprising at least one atmosphere contacting surface having a pollutant treating material thereon.
2. Discussion of the Related Art
A review of literature relating to pollution control reveals many references discussing the general approach of cleaning waste gas streams entering the environment. If too much of one pollutant or another is detected as being discharged, steps are taken to reduce the level of that pollutant, either by treating the gas stream or by modifying the process that produces the pollutant. However, there has been little effort to treat pollutants which are already in the environment; the environment has been left to its own self cleansing systems.
U.S. Pat. No. 3,738,088 discloses an air filtering assembly for cleaning pollution from the ambient air by utilizing a vehicle as a mobile cleaning device. A variety of elements are used in combination with a vehicle to clean the ambient air as the vehicle is driven through the environment. In particular, modified vehicles include ducting to control air stream velocity and direct the air to a variety of filters, electronic precipitators and catalyzed postfilters.
German Patent DE 43 18 738 C1 also discloses a process for the physical and chemical cleaning of outside air. Motor vehicles are used as carriers of conventional filters and/or catalysts, which do not constitute operational components of the vehicle but are used to directly clean atmospheric air.
Another approach is discussed in U.S. Pat. No. 5,147,429, which is directed to a mobile airborne air cleaning station. In particular, this patent features a dirigible for collecting air with a plurality of different types of air cleaning devices contained therein. The air cleaning devices disclosed include wet scrubbers, filtration machines, and cyclonic spray scrubbers.
The difficulty with devices previously disclosed for cleaning ambient air in the atmosphere is that they require new and additional equipment, and may be required to be operated separately just to accomplish such cleaning. For example, the modified vehicle disclosed in U.S. Pat. No. 3,738,088 requires separate ducting and filters, and the equipment laden dirigible of U.S. Pat. No. 5,147,429 is operated solely for such cleaning purposes.
German patent DE 40 07 965 C2 to Klaus Hager discloses a catalyst comprising copper oxides for converting ozone and a mixture of copper oxides and manganese oxides for converting carbon monoxide. The catalyst can be applied as a coating to a self heating radiator, oil coolers or charged-air coolers. The catalyst coating comprises heat resistant binders which are also gas permeable. It is indicated that the copper oxides and manganese oxides are widely used in gas mask filters and have the disadvantage of being poisoned by water vapor. However, the heating of the surfaces of the automobile during operation evaporates the water. In this way, continuous use of the catalyst is possible since no drying agent is necessary.
Manganese oxides are known to catalyze the oxidation of ozone to form oxygen. Many commercially available types of manganese compound and compositions, including alpha manganese oxide are disclosed to catalyze the reaction of ozone to form oxygen. In particular, it is known to use the cryptomelane form of alpha manganese oxide to catalyze the reaction of ozone to form oxygen.
Alpha manganese oxides are disclosed in references such as O'Young, Hydrothermal Synthesis of Manganese Oxides with Tunnel Structures, Modern Analytical Techniques for Analysis of Petroleum, presented at the Symposium on Advances in Zeolites and Pillared Clay Structures before the Division of Petroleum Chemistry, Inc. American Chemical Society New York City Meeting, Aug. 25-30, 1991 beginning at page 348. Such materials are also disclosed in U.S. Pat. No. 5,340,562 to O'Young, et al. Additionally, forms of .alpha.-MnO.sub.2 are disclosed in McKenzie, the Synthesis of Birnessite, Cryptomelane, and Some Other Oxides and Hydroxides of Manganese, Mineralogical Magazine, December 1971, Vol. 38, pp. 493-502. For the purposes of the present invention, .alpha.-MnO.sub.2 is defined to include hollandite (BaMn.sub.8 O.sub.16.xH.sub.2 O), cryptomelane (KMn.sub.8 O.sub.16.xH.sub.2 O), manjiroite (NaMn.sub.8 O.sub.16.xH.sub.2 O) and coronadite (PbMn.sub.8 O.sub.16.xH.sub.2 O). O'Young discloses these materials to have a three dimensional framework tunnel structure (U.S. Pat. No. 5,340,562 and O'Young Hydrothermal Synthesis of Manganese Oxides with Tunnel Structures both hereby incorporated by reference). For the purposes of the present invention, .alpha.-MnO.sub.2 is considered to have a 2.times.2 tunnel structure and to include hollandite, cryptomelane, manjiroite and coronadite.
Commonly assigned U.S. Pat. No. 5,422,331, incorporated herein by reference, discloses methods and catalyst compositions for abating noxious substances, particularly ozone, contained in air. The treatment of carbon monoxide, hydrogen sulfide and hydrocarbons is also discussed. A primary focus of this patent is methods of treating air taken into and/or circulated in aircraft cabins, with the cabins of trains, buses and other vehicles being mentioned as well. The patent also indicates that the disclosed catalysts can be used to abate ozone in equipment, such as xerographic copy machines, which generate ozone. Further, the patent indicates that the catalysts can be applied to surfaces in air handling systems for residences, office and factory buildings, public buildings, hospitals and the like. For this method, the catalyst can be applied to existing substrates of the air handling system, such as fan blades in air handling fans or compressors, grills, louvers or any other surface exposed to the air stream.
Responsive to the difficulties associated with devices for proactively treating the atmosphere, the Assignee herein in U.S. Appl. Ser. No. 08/410,445, filed Mar. 24, 1995, disclosed apparatus and related methods for treating the atmosphere by employing a moving vehicle. In preferred embodiments a portion of the cooling system (e.g. the radiator) is coated with a catalytic or adsorption composition. Additionally, a fan associated with the cooling system can operate to draw or force air into operative contact with the radiator. Pollutants contained within the air such as ozone and/or carbon monoxide are then converted to non-polluting compounds (e.g. oxygen gas and carbon dioxide).
U.S. Appl. Ser. No. 08/412,525 ('525), of which the present application is a continuation-in-part, discloses methods and apparatus for treating pollutants present in the atmosphere, by the use of a stationary substrate coated with pollutant treating composition. The present application is directed to particular embodiments of the invention set forth in the '525 application, directed at coating various surfaces which contact the atmosphere with pollution treating compositions.